Burr hole caps and methods of use

ABSTRACT

In one embodiment, an apparatus comprises: a base structure adapted to be inserted within the burr hole; a lead securing member for securing the lead, the lead securing member comprising a first arm structure and a second arm structure, at least one spring loaded structure adapted to exert a force to bring the first arm structure and the second arm structure together; and a positioning tool having a distal end adapted to be inserted within the lead securing member. When the positioning tool is positioned within the lead securing member, the distal end holds the first and second arm structures a sufficient distance apart to receive a lead between the first and second arm structures; wherein the positioning tool comprises a control structure at a proximal end that, when engaged, causes the distal end of the positioning tool to be released from between the first and second arm structures.

RELATED APPLICATION

The present application claims the benefit of U.S. ProvisionalApplication Ser. No. 60/794,326, entitled “BURR HOLE CAP AND METHODS OFUSE,” filed Apr. 21, 2006, which is incorporated herein by reference.

TECHNICAL FIELD

The present application is generally related to an apparatus for holdinga stimulation lead, catheter, or cannula within a burr hole.

BACKGROUND

Deep brain stimulation (DBS) refers to the delivery of electrical pulsesinto one or several specific sites within the brain of a patient totreat various disorders. For example, DBS has been proposed as aclinical technique for treatment of chronic pain, essential tremor,Parkinson's disease (PD), dystonia, epilepsy, depression,obsessive-compulsive disorder, and other disorders.

A DBS procedure typically involves first obtaining preoperative imagesof the patient's brain (e.g., using computer tomography (CT) or magneticresonance imaging (MRI)). The imaging process sometimes involves firstaffixing to the patient's skull fiducial markers that are discernable onthe images produced by the imaging process. The fiducial markers assistin registering the preoperative images to the actual physical positionof the patient in the operating room during the subsequent surgicalprocedure. Using the preoperative images, the neurosurgeon can select atarget region within the brain, an entry point on the patient's skull,and a desired trajectory between the entry point and the target region.The entry point and trajectory are carefully selected to avoidintersecting or otherwise damaging critical brain structures.

In the operating room, the patient is immobilized and the patient'sactual physical position is registered. The physician marks the entrypoint on the patient's skull and drills a burr hole at that location. Amechanism is provided to precisely control the path through thepatient's brain to the desired location. Specifically, a positioningerror on the order of a millimeter can have a significant negativeeffect on the efficacy of the DBS therapy. Stereotactic instrumentationand trajectory guide devices are commercially available products thatfacilitate the control of the trajectory and positioning of a leadduring the surgical procedure.

A microdrive introducer can be used to insert a deep brain stimulationlead toward the selected region of the brain along the selectedtrajectory. The lead provides one or several conductive paths to deliverstimulation pulses to the selected region. The lead includes a verysmall diameter insulative lead body with one or several conductors(e.g., stranded wires) embedded in the insulative material. The leadalso includes one or several electrodes at a distal end of the lead thatare electrically coupled to respective conductors. The electrodes can beused to record signals within the brain and/or to deliver electricalstimulation pulses to brain tissue. Often, the electrical activityadjacent to one or several electrodes is analyzed to determine whetherthe recorded signals are consistent with the targeted region of thebrain. If the recorded signals are not consistent with the targetedregion, an adjustment to the lead's position can be made as appropriate.

A burr hole plug or cap structure is typically utilized to retain thelead in the desired position. A burr hole structure generally includes(i) a ring or grommet-like element that is inserted into the hole firstso as to protect the edges of the burr hole and (ii) a cap or plugdevice that is inserted into the ring or grommet-like element to securethe lead and plug the hole.

By way of example, in U.S. Pat. No. 6,044,304, a burr ring is disclosedthat is secured to the skull. The burr hole plug of the '304 patent alsohas an upper flange portion and circumferential ribs used to positionthe plug in the cranium. Also, the burr hole plug described in the '304patent includes an aperture capable of accepting a lead through aseptum.

In U.S. Pat. No. 5,954,687, a device is disclosed for securing acatheter within a burr hole. The device has a series of spaced septumelements that can be selectively penetrated for fluid communication witha reservoir in the apparatus. The main objective of the device is toallow fluid access to the patient's brain through a burr hole. Anchoringof the device is not taught and there are a limited predetermined numberof septum holes that can be accessed.

U.S. Pat. No. 5,927,277 describes a burr hole ring for retaining a proberelative to the skull. The burr hole ring has an engaging member withholes to receive a probe. The '277 patent also describes a method forsecuring a device at a desired orientation within the burr hole. Since afixed spacing between holes is described, the device can be placed in alimited number of locations through the burr hole.

U.S. Pat. No. 5,865,842 discloses a system and method for anchoring alead in a burr hole. The disclosed system consists of a base-plate,adaptor, seal, and screw cap. The lead is anchored mechanically at theburr hole at a 90 degree angle relative to the burr hole.

U.S. Pat. No. 5,843,150 discloses an annular clamping means with acompressible feed-through member for receiving a lead. The describedorder for anchoring the lead includes making the burr hole, insertingthe plug ring, inserting the lead, and engaging the clamping member.

Other burr hole plug assemblies and features of burr hole plugs aretaught in U.S. Pat. No. 5,464,446 (burr hole plug with a central lumenand a cap that engages with the flange of the plug); U.S. Pat. No.4,998,938 (a device that facilitates insertion of an instrument into apatient's cranial cavity); U.S. Pat. No. 4,328,813 (a burr hole plugwith a cap that anchors the lead); and U.S. Pat. No. 4,245,645 (a probeand system that is used to perform stereoelectroencephalographicexploration).

SUMMARY

In one embodiment, an apparatus for securing a lead within a burr hole,comprises: a base structure adapted to be at least partially insertedwithin the burr hole; a lead securing member for securing the leadwithin the burr hole, the lead securing member comprising a first armstructure and a second arm structure, at least one spring loadedstructure adapted to exert a force to bring the first arm structure andthe second arm structure together; and a positioning tool having adistal end adapted to be inserted within the lead securing member;wherein when the distal end of the positioning tool is positioned withinthe lead securing member, the distal end holds the first and second armstructures a sufficient distance apart to receive a lead between thefirst and second arm structures; wherein the positioning tool comprisesa control structure at a proximal end that, when engaged, causes thedistal end of the positioning tool to be released from between the firstand second arm structures thereby allowing further contraction of thefirst and second arm structures to secure the lead.

The foregoing has outlined rather broadly certain features and/ortechnical advantages in order that the detailed description that followsmay be better understood. Additional features and/or advantages will bedescribed hereinafter which form the subject of the claims. It should beappreciated by those skilled in the art that the conception and specificembodiment disclosed may be readily utilized as a basis for modifying ordesigning other structures for carrying out the same purposes. It shouldalso be realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the appendedclaims. The novel features, both as to organization and method ofoperation, together with further objects and advantages will be betterunderstood from the following description when considered in connectionwith the accompanying figures. It is to be expressly understood,however, that each of the figures is provided for the purpose ofillustration and description only and is not intended as a definition ofthe limits of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a burr hole assembly according to one representativeembodiment.

FIG. 2 depicts an outer ring structure adapted to be placed within theburr hole of the patient according to one representative embodiment.

FIG. 3 depicts a grasping member adapted to fit around the lead and tobe placed within the outer ring of FIG. 2 according to onerepresentative embodiment.

FIG. 4 depicts a wedge member structure for placement around thegrasping member of FIG. 3.

FIG. 5 depicts burr hole device that enables a lead to be secured withina burr hole according to another representative embodiment.

FIG. 6 burr hole device according to another representative embodiment.

FIG. 7 depicts a placement tool coupled to a burr hold device for use inmoving and manipulating a burr hole device according to onerepresentative embodiment.

FIG. 8 depicts the placement tool in isolation according to onerepresentative embodiment.

DETAILED DESCRIPTION

Although a number of burr hole devices have been made commerciallyavailable, many burr hole cap devices suffer from various limitations.For example, some commercially available burr hole devices are toosimple in design and do not provide adequate stabilization of the leadwith the burr hole. Alternatively, other commercially available burrhole devices that achieve the desired stabilization of the lead withinthe burr hole are quite cumbersome during the placement and manipulationto capture the lead within the burr hole. Specifically, burr holes arerelatively small, e.g., typically about 14 mm. Accordingly, theindividual elements of a burr hole device can be quite small. Thus, whenburr hole devices require precise manipulations, the lead securingprocess can be quite tedious. In contrast, representative embodimentsprovide burr hole devices that provide a desired amount of stabilizationof the lead without requiring undue and cumbersome manipulation of smallconstituent elements.

FIG. 1 depicts burr hole 100 assembly according to one representativeembodiment. For the sake of clarity, the actual cap for the burr holeassembly is omitted to enable the interior details of assembly 100 to beshown in FIG. 1. As shown in FIG. 1, burr hole cap assembly comprises100 outer ring 101, wedge member 102, and grasping member 103.

In one embodiment as shown in FIG. 2, outer ring 101 is adapted to beplaced within the burr hole of the patient. Outer ring 101 possesses asmall profile somewhat flat portion that is intended to remain on thepatient's skull and an annular portion adapted to be inserted within theburr hole. Additionally, outer ring 101 is preferably fabricated from abio-stable, bio-compatible polymer material. Outer ring 101 preferablypossesses some amount of rigidity and strength to promote mechanicalrobustness and stability. Outer ring 101 includes apertures 201 forreceiving bone screws to secure outer ring 101 to the patient's skullafter outer ring 101 has been placed with the burr hole. In theembodiment shown in FIG. 2, outer ring 101 comprises securing members202 into which a cap structure (not shown) can be coupled.

In one embodiment as shown in FIG. 3, grasping member 103 is adapted tofit around the lead and to be placed within the outer ring 101 withrelatively little difficulty. For the purpose of this application, theterm “lead” is used in a broad sense and encompasses electricalstimulation leads, drug infusion catheters, cannulas, and any othersimilar elongated medical device to be stabilized within a burr hole ofa patient. As shown in FIG. 3, grasping member 103 is a somewhat annularstructure. Grasping member 103 could alternatively be tapered or possessa truncated cone-shape to facilitate the assembly of burr hole capassembly 100. Grasping structure 301 comprises gap 301 that runs along asubstantial portion of the diameter of grasping member 103. Preferably,grasping member 103 is a single integral structure and gap 301 is onlycompletely open on only one side of grasping member 103. Additionally,grasping member 103 is preferably fabricated of a bio-compatible andbio-stable material that possesses a relatively low durometer to causegrasping member 103 to be compressible. For example, grasping member 103can be fabricated from a suitable silicone material.

In use, when a lead is positioned within the burr hole of a patient,grasping member 103 is placed around the lead using gap 301. Whengrasping member 103 is not compressed, gap 301 possesses a width that issufficiently greater than the diameter of the lead to preventapplication of an excessive frictional force on the lead. Thus, graspingmember 103 can be placed on the lead at a distance away from theposition where outer ring 101 is secured to the skull. Then, graspingmember 103 can be slid along the lead and into the outer ring withoutdislocating the lead within the patient. The outside diameter ofgrasping member 103 is preferably smaller that the inside diameter ofouter ring 101 thereby allowing the insertion of grasping member 103into outer ring 101 to occur with little complication.

After grasping member 103 is placed around the lead and within outerring 101, wedge member 102 (as shown in isolation in FIG. 4) is placedaround grasping member 103 and within outer ring 101 to form theassembly shown in FIG. 1. Wedge member 102 preferably possesses adurometer that is greater than the durometer of grasping member 103.Additionally, wedge member 102 preferably possesses an inner diameterthat is smaller than the outside diameter of grasping member 103.Accordingly, when wedge member 102 is placed around grasping member 103,wedge member 102 compresses grasping member 103 thereby narrowing gap301 and securing the lead.

FIG. 5 depicts another burr hole device that enables a lead to besecured within a burr hole with a relatively minimal amount ofdifficulty. As shown in FIG. 5, burr hole device 500 includes outer ring501 which is preferably implemented in a manner similar to outer ring101. Inner disc 502 is adapted to be placed within outer ring 501 andaround the lead. Preferably, outer ring 501 possesses interior flange oredge 506 to hold inner disc 502. Also, inner disc 502 is preferablyrotatable within outer ring 501 to enable the lead to be captured fromsubstantially any position within the burr hole. Inner disc 502preferably comprises a first arm structure 505 that is rigidly fixed oninner disc 502. Second arm structure 503 is preferably attached tomoveable curved projection element 504 which thereby allows a “window”507 of space through burr hole device 500 to be opened and closed.

In use, with second arm structure 503 positioned such that window 507 isas wide as possible, inner disc 502 is placed within outer ring 501 suchthat the lead is positioned between arms 503 and 505. Inner disc 502 isthen rotated within outer ring 501 by pushing a suitable tool againstrigid arm 505 until rigid arm 505 is positioned against the lead. Byimplementing rigid arm 505 to protrude above the main surface of innerdisc 502, rigid arm 505 can be used to rotate disc 502 within ring 501.Thereby, the manipulation of disc 502 into the correct position canoccur in an efficient manner and cumbersome precision movements are notrequired. Then, arm 503 is rotated toward arm 505 to secure the leadbetween arms 503 and 505.

FIG. 6 depicts burr hole device 600 according to another embodiment.Burr hole device 600 is similar to burr hole device 500 in that the leadis secured between arms 603 and 604. Burr hole device 600 differs fromburr hole device 500 in the manner in which arms 603 and 604 are broughttogether to secure the lead.

As shown in FIG. 6, burr hole device 600 comprises annular structure 601that is inserted within the burr hole of the patient and secured to thepatient's skull. On the interior wall of annular structure 601, a lowerflange or edge can be provided to hold lead securing member 602. Also,annular structure 601 may comprise ridges or other structures on itsinterior wall to limit the rotation of lead securing member 602.

In use, tool 609 is initially inserted within lead securing member 602.Upper lever structures 605 and 606 (e.g., “dead bolts”) are springloaded such that lever structures 605 and 606 exert an “inward” forceagainst arms 603 and 604, respectively. Although spring loaded leverstructures are shown for one embodiment, other shape memory elementscould be employed. For example, suitable shaped wire elements havingspring characteristics could be employed in lieu of spring loaded leverstructures. When the distal end of tool 609 is inserted within leadsecuring member 602, arms 603 and 604 clamp against the distal end oftool 609 as shown in FIG. 6. The distal end of tool 609 maintains anopening 610 (between arms 603 and 604) large enough to accept the leadwith or without a cannula with little difficulty. Also, the clampingforce applied by arms 603 and 604 against tool 609 allows lead securingmember 602 to be moved and manipulated into place by using tool 609 (seeFIG. 7). Additionally, when inserted within lead securing member 602,the distal end of tool 609 maintains spring loaded lever structures 607and 608 in a “closed” position. That is, lever structures 607 and 608are spring loaded to automatically open and contact an inner shoulder ofannular structure 601 when the distal end of tool 609 is removed. Theexpansion or opening of lever structures 607 and 608 causes securingmember 602 to be secured within annular structure 601.

FIG. 7 depicts an expanded view of tool 609 inserted within securingmember 602. As shown, a surgeon can grasp tool 609 to pick-up and movesecuring member 602 for placement within annular structure 601 withrelative ease. Once, lead securing member 602 is positioned around thelead and within the annular structure, the surgeon need only remove tool609 from lead securing member 602 to secure the lead and lock member 602into place against annular structure 601. Specifically, as the distalend of tool 609 is removed, arms 603 and 604 clamp around the lead (orthe cannula) due to the application of force exerted by spring loadedlever structures 605 and 606. Also, as tool 609 is removed, spring loadlever structures 607 and 608 expand to contact annular structure 601.

FIG. 8 depicts another view of tool 609. As shown in FIG. 8, tool 609comprises handles 801 and 802 at is proximal end. When handles 801 and802 are compressed together, pin 803 is extended from the distal end of609. Pin 803 is used to remove the distal end of tool 609 from annularstructure 601. Specifically, when extended, pin 803 contacts an interiorsurface of annular structure 601 thereby pushing end 804 of tool 609upward. When end 804 is pushed upward, arms 603 and 604 are no longerheld apart by end 804 and arms 603 and 604 contract toward each other toclamp around the lead. Additionally, end 804 is tapered to allow end 804to be re-inserted within annular structure 601 to push arms 603 and 604apart and to retract lever structures 607 and 608. Accordingly, leadsecuring member 602 can be removed from annular structure 601 asefficiently as it can be inserted with structure 601.

Although representative embodiments and advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the appended claims. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. As one of ordinaryskill in the art will readily appreciate from this disclosure,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized without departing from the scope of the appended claims.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

1. A kit for securing a lead within the skull of a patient, the kitcomprising: a base structure adapted to be at least partially insertedwithin a burr hole; a lead securing member, for placement within thebase structure, comprising (i) a substantially cylindrical body, (ii) anopen slot in the cylindrical body, (iii) an aperture, in the cylindricalbody, adjacent to the open slot, and (iv) first and second armstructures disposed on respective sides of the open slot, the first andsecond arm structures having proximal ends located interior to thecylindrical body and distal ends at an edge of the cylindrical body, thefirst and second arm structures subjected to a contracting biasingforce, the first and second arm structures being pivotally mounted atrespective mounting points, the aperture being disposed above theproximal ends of the first and second arm structures; and a positioningtool comprising (i) a distal end adapted to be inserted within theaperture, (ii) a pin disposed within the distal end, and (iii) a controlstructure for causing the pin to extend out from the distal end of thepositioning tool; wherein, when the distal end of the positioning toolis disposed within the aperture of the lead securing member, (i) thefirst and second arm structures clamp to the distal end with sufficientforce to permit the positioning tool to lift and place the lead securingmember and (ii) the distal end of the positioning tool maintains thefirst and second arms apart to permit placement of a stimulation leadwithin the slot of the lead securing member; wherein, when the controlstructure of the positioning tool is actuated, the pin of thepositioning tool is extended to force the distal end of the positioningtool from between the first and second arm structures to release thelead securing member from the positioning tool.
 2. The kit of claim 1wherein the lead securing member further comprises: first and secondbolt structures, the first and second bolt structures being springbiased to extend radially from an outer surface of the cylindrical bodyto lock the lead securing member against the base structure.
 3. The kitof claim 2 wherein the positioning tool maintains the first and secondbolt structures within the cylindrical body when the distal end of thepositioning tool is disposed within the aperture of the lead securingmember.
 4. The kit of claim 1 wherein the base structure comprisesridges along its interior surface to limit rotation of the lead securingmember within the base structure.
 5. The kit of claim 1 wherein thecontrol structure of the positioning tool comprises a push-button thatis depressible against a handle of the positioning tool.
 6. The kit ofclaim 1 wherein the base member comprises a lower flange for contactwith a bottom surface of the lead securing member.
 7. The kit of claim 1wherein the first and second arm structures are engaged by spring-loadeddead bolts to apply the biasing force to the first and second armstructures.
 8. The kit of claim 1 wherein the first and second armstructures are engaged by spring-shaped wire structures to apply thebiasing force to the first and second arm structures.